The present invention relates to a cutting insert for chip forming machining, primarily milling.
A known cutting insert for chip forming machining is disclosed in U.S. Pat. No. 4,710,069, the disclosure includes at least one cutting edge created by the intersection between an upper face and an edge face of the cutting insert. The upper face defines a rake face and the edge face defines a clearance face. The rake face includes a chip upsetting face disposed adjacent to the cutting edge, and a curved chip forming face contiguous with the chip upsetting face. A border line or edge separates the chip upsetting face from the chip forming face. A number of depressions extend inwardly from the chip forming face and are spaced apart in a direction parallel to the cutting edge. The depressions are arranged to bridge the transition line between the chip upsetting face and the chip forming face. During the chip flow, the underside of the chip engages the depressions, whereby beads or runners are formed on the chip underside. This working of the chip produces heating of the chip to facilitate chip deformation.
In that cutting insert, the depressions extend in a direction perpendicular to the cutting edge of the cutting insert. The chip does not travel perpendicularly relative to the transition line, but rather is angled from the perpendicular by a so-called chip flow angle (described hereinafter in connection with FIG. 3), usually of about 5.degree. to 15.degree.. Hence, the chip will be pressed against the sides of the depressions to produce increased friction between the chip and the cutting insert. The friction generates heat, which is transmitted to the insert, thereby causing an unwanted heating of the cutting insert takes place. Such heating will eventually damage the cutting insert.
An object of the present invention is to provide a cutting insert which avoids the negative effects described above by causing the chip to flow in a way producing a smaller contact area and consequently less friction between the chip and the cutting insert.